Suggest Treatment For Pain And Numbness In Legs After Discectomy

I had two discectomy at L4 - L5 in 2005 and i recovered very well and my life was like any normal man. the I had lumbar fusion L4-L5 - S1 in 2010 after the car accident. few months after the surgery were fine and now my life is like hell. I have pain, numbness, feel pins in my both legs, feet and lower back. I can't walk without walker. I can walk maximum 5 - 10 minutes only. I can't sit or lay more than 15 - 20 minutes. I take narcotic medicine morphine for pain, and antidepressant for anxiety, depression, panic attacks. After the surgery i got erection dysfunction problem. I can't get erection and had only one time sex with my wife after few weeks of lumbar fusion.My family doctor gave me Viagra but it was useless. I don't know what to do? is it possible that during the lumbar fusion surgery my nerves got damage?